In a mobile communication system that utilizes a spread spectrum system, there has been used a technique called a RAKE receiving system for improving communication quality. In this receiving system, a plurality of data received via different communication paths are demodulated in circuits called fingers and these demodulated data are combined. In the RAKE receiving system, a weight is added to each of output signals from the fingers in some way when the demodulated data are combined. Generally, the weighting is often carried out on the basis of power of the receive data.
FIG. 6 shows an example of a schematic diagram of a conventional RAKE combining circuit.
The RAKE combining circuit 50 shown in FIG. 6 has three fingers (Finger 0, Finger 1 and Finger 2) 52a, 52b and 52c for demodulating receive data, three multipliers 54a, 54b and 54c corresponding to the three fingers 52a, 52b and 52c, and an adder 56 for adding up output signals from these three multipliers 54a, 54b and 54c. 
In the illustrated RAKE combining circuit 50, the receive data of respective paths are demodulated by the respective fingers 52a, 52b and 52c. As described above, the demodulated receive data S0, S1 and S2 of the respective paths are multiplied by weight factors W0, W1 and W2 generated on the basis of the power of the receive data by the corresponding multipliers 54a, 54b and 54c so as to give a weight to the demodulated receive data. Then the weighted data are added up and combined by the adder 56 before being outputted as a signal SYMOUT.
However, since a random noise component, an interfering component and the like may be contained in the receive data in a case that the respective demodulated receive data are given the weight on the basis of the power of the receive data, the receive data are not always combined accurately at an expected signal component ratio. Moreover, phases of the receive data itself may be also rotated under an influence of fading or the like. Generally, the phase shift of the receive data is estimated by using a pilot symbol whereby to perform a process of correcting the receive data. However, there is a possibility that the estimated value itself may have errors then.